LAUSR

Abstract A new Schiff base ligand was synthesized by the reaction of 4-acetyl-5,6-diphenyl-3(2H)-pyridazinone with ethylenediamine. A series of binary copper(II) Schiff base complexes have been synthesized by using various copper(II) salts; AcO − , NO 3 − , ClO 4 − , Cl − and Br − . Ternary complexes were synthesized by using auxiliary ligands (L′) [N,O-donor; 8-hydroxyquinoline and glycine or N , N -donor; 1,10-phenanthroline, bipyridyl and 2-aminopyridine]. The structures of the Schiff base and its complexes were characterized by elemental and thermal analyses, IR, electronic, mass, 1 H NMR and ESR spectra in addition to conductivity and magnetic susceptibility measurements. The obtained complexes include neutral binuclear complexes as well as neutral and cationic mononuclear complexes according to the anion used and the experimental conditions. The ESR spin Hamiltonian parameters of some complexes were calculated and discussed. The metal complexes exhibited octahedral and square planar geometrical arrangements depending on the nature of the anion. Kinetic parameters (Ea, A, ΔH, ΔS and ΔG) of the thermal decomposition stages were evaluated using Coats–Redfern equations. The antimicrobial activity of the Schiff base and its complexes was screened against Gram–positive bacteria ( Staphylococcus aureus and Bacillus subtilis ), Gram–negative bacteria ( Salmonella typhimurium and Escherichia coli ), yeast ( Candida albicans ) and fungus ( Aspergillus fumigatus ). The antitumor activity of the Schiff base and some of its Cu(II) complexes was investigated against HepG-2 cell line.